Abstract : A 9-year survey on 500,000 Great Lakes naval recruits indicated that only 2 men per 1000 (0.2 percent) had no previous history of dental caries experience at the time of entrance into the Navy. The annual incidence of caries-free men ranged from a low of 1.3 per 1000 in 1967 to a high of 3.1 per 1000 in 1963. Marked variations in the prevalence of caries-free men from different geographic regions of the United States were observed. Correlation analysis indicated that these variations were partly related to the availability of natural fluoride in public water supplies. (Author)